Andy breathed freer.

“Oh, I agree with you there,” he hastened to say; “and I’m glad you hadn’t any more serious reason.  But did you ever see such a picture in all your born days?  Just look at the forest bordering the river.  Think of trying to push through such a dense mass of over-grown jungle.  And I bet it’s just full of snakes, poisonous spiders, lizards and all such things.”

“Not to mention such trifling citizens as jaguars, ocelots, tapirs, alligators, crocodiles and their kind,” laughed Frank.

“Ugh! what lucky fellows we are to be away up here, where we can skim along at the rate of thirty miles an hour easily, without half trying, and snap our fingers at all those things.  I tell you, Frank, this aviation business is the greatest thing that ever came down the pike.”

So they continued from time to time to converse as they kept pushing along, following the winding course of the swollen river that could be plainly seen below, between its banks of forest.

Frank did not soar high at this time.  There seemed no need, and besides, both of the boys were deeply interested in watching the various changes that kept taking place in the checkerboard landscape below.

Several times during the first hour they passed over hamlets or villages.  On such occasions it was ludicrous to observe the excitement that occurred.  The Bird boys would not have been true to their nature had they not enjoyed the tremendous sensation which the sudden and unheralded appearance of the aeroplane caused in these river settlements.

Loud shouts floated up to them that constantly grew in volume.  Men yelled, women and children screamed.  Many fell flat on their faces; others tried to conceal themselves, as though they belonged to a covey of wild ducks over which a hungry eagle hovered, picking out his contemplated dinner.

And the last thing Andy would see, as he looked back, would be wildly running figures gesticulating furiously and evidently next door to crazy with excitement.  Apparently these natives believed that the aeroplane must be a visitor from another world, or else some monster bird of a family long understood to be extinct.

The second hour had nearly ended and everything seemed to be moving along smoothly.  Frank saw not a cloud on the horizon thus far.  Surely this augured well for the ultimate success of their strange expedition.

Suddenly he heard Andy give vent to a cry of alarm.

“What is it?” he demanded, quickly.

“Turn her upward, quick!  They are going to shoot at us!” shouted the other.

Frank instantly started to obey, and while their forward progress still continued unabated, the aeroplane commenced to head toward a higher altitude.

Immediately he heard the dull report of a gun from below.  He dared not bend his head to look, since all his attention was needed to take care of his machine at such a critical moment.  But the whine of the bullet as it passed close by was very plainly heard.